1. Field of the Invention
The present invention relates to a semiconductor device and a semiconductor package including the semiconductor device, and more particularly relates to a semiconductor device including a plurality of data input/output (I/O) pads and a semiconductor package including the semiconductor device.
2. Description of Related Art
In a semiconductor device, such as a DRAM (Dynamic Random Access Memory), the number of pads is increasing with sophistication of its functionalities. For example, as the number of data bits that can be input or output at a time increases, the number of data I/O pads needs to be increased, which results in an increase of the total number of pads.
However, as opposed to the size of a transistor and a wiring pitch, which are downscaled year by year, pads are not so downsized. One of the methods for downsizing is to arrange a plurality of pads in two lines instead of arranging them in one line (see Japanese Patent Application Laid-open No. 2006-278805).
However, in a semiconductor device described in Japanese Patent Application Laid-open No. 2006-278805, there exists an area in which two data I/O pads (DQ) are arranged adjacent to each other. By arranging the data I/O pads adjacent to each other, two data wirings are arranged extending close to each other on a package substrate on which a semiconductor device is mounted, and this may cause a coupling noise in the area. To prevent the coupling noise, it is desired to make a shield by arranging a power supply pad on both sides of each of the data I/O pads.
Meanwhile, a data I/O buffer that drives a data I/O pad is likely to generate a power supply noise. Accordingly, the data I/O buffer often employs an independent power supply that is different from power supplies for other peripheral circuits. In addition, because the data I/O buffer has large instantaneous power consumption, an output power supply pad (VDDQ or VSSQ) is assigned to each of one or more data I/O buffers.
In this case, as the output power supply pads (VDDQ and VSSQ) are arranged both sides of the one or more data I/O buffers (DQ) and these are arranged as a unit in a repeated manner, it becomes possible to prevent the coupling noise. However, with this method, the number of necessary power supply pads (VDDQ and VSSQ) excessively increases as the number of data I/O pads (DQ) increases.